ISRN Astronomy and AstrophysicsVolume 2013 (2013), Article ID 201235, 8 pageshttp://dx.doi.org/10.1155/2013/201235

Research Article

BVRcIc Observations and Analysis of the Near-Contact Solar Type Eclipsing Binary, V530 Andromedae

Ronald G. Samec,1,2 Daniel Flaaten,¹ James Kring,1,2 and Danny R. Faulkner2,3,4

¹Astronomy Group, Department of Physics and Engineering, Bob Jones University, Greenville, SC 29614, USA²Lowell Observatory, Flagstaff, AZ 86001, USA³University of South Carolina, Lancaster, SC 29720, USA⁴Johnson Observatory, Petersburg, KY 41080, USA

Received 3 August 2013; Accepted 8 September 2013

Academic Editors: F. Arenou, A. Pamyatnykh, and A. Sesana

Copyright © 2013 Ronald G. Samec et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract.

We present the first precision UBVRcIc light curves, an initial period study, and a simultaneous light curve solution for the near-contact solar type eclipsing binary V530 And. Our observations were taken with the 0.81 m Lowell reflector on 27 and 29 September, 2011, with time being granted from the National Undergraduate Research Observatory (NURO). Our Wilson Devinney Program solution yields a semidetached, V1010 Oph configuration: the more massive component is filling its Roche lobe. The system is apparently approaching contact for the first time. It is not a classic Algol.

1. History

V530 And [2MASS J01274106 + 3351552, NSVS 6447718, TYC 2300-116-1, (2000) = 01 h 27 m 41.050 s, (2000) = +33° 51′ 55.47′′ ICRS, , , ] was discovered by Khruslov (2008) [1]. It was designated as EB with a 12.6–13.3 R-magnitude range () with the ephemeris: Their light curve is given as Figure 1.

Figure 1: Light curve for V530 And from Khruslov (2008) [1].

V530 And was observed by the Robotic Optical Transient Search Experiment [2] and found to have a period = 0.57721 d and a mean unfiltered magnitude of 12.769. A light curve amplitude of 0.633 mag was determined. It was stated that the light curve was calculated to be in the Fourier region where Lyrae (EB) types are expected. Finally, V530 And appeared in the 80th namelist of variable stars (IBVS #5969, 2011). It was also designated as an EB type. EB binaries are very close together producing distorted curves from tidal and Coriolis forces, but the stars are not in contact, so their light curves still maintain dissimilar eclipse depths.

2. Observations

This system was observed as a part of our student/professional collaborative studies of interacting binaries from data taken from NURO observations (National Undergraduate Research Observatory). Our light curves were taken with the Lowell 0.81 m reflector in Flagstaff with a CRYOTIGER cooled (<−100°C) NASACAM and a CCD chip with standard UBVRcIc filters. Observations were taken on 27 and 29 September, 2011, by Samec, Kring, and Faulkner. The time was awarded by the Lowell TAC as a part of the time allocated from NURO. Analyses were done by Flaaten and Samec. The individual observations included 92 in the -filter, 93 in , 92 in , and 91 in and . The standard error of a single observation was 3 mmag in and , 2 mmag in and , and 4 mmag in . Our observations are given in Table 1, in delta magnitudes, , , , and in the sense of variable minus comparison star.

Table 1: Photometry of V530 And.

2455800+
2455800+
2455800+
2455800+
2455800+

1.066
30.6497
1.269
30.7671
1.034
30.8610
1.384
32.6971
1.148
32.8347

1.100
30.6569
1.224
30.7736
1.035
30.8669
1.425
32.7031
1.118
32.8411

1.127
30.6642
1.143
30.7868
1.032
30.8728
1.546
32.7142
1.096
32.8470

1.158
30.6714
1.133
30.7937
1.039
30.8794
1.640
32.7225
1.081
32.8529

1.205
30.6796
1.114
30.8003
1.046
30.8853
1.727
32.7292
1.064
32.8587

1.247
30.6874
1.093
30.8070
1.056
30.8912
1.758
32.7350
1.050
32.8645

1.314
30.6958
1.287
32.6839
1.082
30.9016
1.775
32.7417
1.035
32.8728

1.358
30.7035
1.324
32.6899
1.091
30.9075
1.776
32.7475
1.025
32.8786

1.395
30.7108
1.384
32.6971
1.103
30.9133
1.781
32.7546
1.015
32.8857

1.402
30.7174
1.425
32.7031
1.124
30.9193
1.756
32.7604
1.021
32.8915

1.398
30.7244
1.546
32.7142
1.140
30.9251
1.704
32.7669
1.010
32.8974

1.397
30.7309
1.640
32.7225
1.160
30.9310
1.619
32.7727
1.011
32.9032

1.388
30.7383
1.133
30.7937
1.188
30.9381
1.549
32.7791
1.030
32.9093

1.395
30.7449
1.114
30.8003
1.765
31.0202
1.473
32.7849
1.023
32.9151

1.352
30.7536
1.093
30.8070
1.112
32.6514
1.401
32.7924
1.036
32.9210

1.309
30.7602
1.083
30.8135
1.140
32.6587
1.340
32.7981
1.058
32.9268

1.269
30.7671
1.079
30.8217
1.165
32.6646
1.290
32.8043
1.052
32.9335

1.224
30.7736
1.057
30.8324
1.202
32.6713
1.257
32.8101
1.054
32.9393

1.143
30.7868
1.048
30.8390
1.229
32.6773
1.220
32.8160
1.064
32.9454

1.352
30.7536
1.042
30.8474
1.287
32.6839
1.194
32.8218
1.086
32.9512

1.309
30.7602
1.032
30.8532
1.324
32.6899
1.168
32.8283
1.123
32.9670

1.134
32.9728

2455800+
2455800+
2455800+
2455800+
2455800+

1.074
30.6520
1.131
30.7892
1.104
30.9215
1.741
32.7497
1.025
32.8667

1.109
30.6593
1.108
30.7961
1.124
30.9274
1.729
32.7568
1.012
32.8750

1.130
30.6666
1.087
30.8027
1.142
30.9333
1.718
32.7626
1.005
32.8808

1.161
30.6738
1.073
30.8093
1.170
30.9404
1.641
32.7691
0.996
32.8879

1.209
30.6820
1.058
30.8159
1.075
32.6452
1.567
32.7749
0.990
32.8937

1.249
30.6897
1.048
30.8240
1.111
32.6536
1.490
32.7813
1.002
32.8996

1.304
30.6982
1.028
30.8348
1.137
32.6609
1.422
32.7871
1.000
32.9054

1.358
30.7059
1.020
30.8414
1.157
32.6669
1.351
32.7945
1.009
32.9115

1.370
30.7132
1.016
30.8496
1.179
32.6735
1.297
32.8003
1.003
32.9173

1.380
30.7198
1.010
30.8555
1.220
32.6795
1.251
32.8065
1.019
32.9232

1.373
30.7267
1.009
30.8633
1.271
32.6862
1.220
32.8123
1.033
32.9290

1.381
30.7333
1.011
30.8691
1.309
32.6921
1.190
32.8182
1.037
32.9357

1.370
30.7407
1.012
30.8750
1.378
32.6994
1.158
32.8240
1.037
32.9415

1.361
30.7472
1.012
30.8817
1.431
32.7054
1.143
32.8305
1.046
32.9476

1.325
30.7560
1.027
30.8875
1.538
32.7164
1.122
32.8369
1.065
32.9534

1.277
30.7626
1.033
30.8934
1.637
32.7247
1.077
32.8433
1.117
32.9692

1.235
30.7694
1.059
30.9039
1.709
32.7314
1.063
32.8492
1.137
32.9750

1.190
30.7760
1.068
30.9097
1.743
32.7372
1.055
32.8551

1.160
30.7826
1.052
30.9156
1.746
32.7439
1.032
32.8609

2455800+
2455800+
2455800+
2455800+
2455800+

1.128
30.6529
1.175
30.7901
1.121
30.9163
1.739
32.7504
1.072
32.8674

1.157
30.6602
1.147
30.7970
1.142
30.9222
1.734
32.7575
1.057
32.8757

1.181
30.6675
1.132
30.8036
1.168
30.9281
1.722
32.7633
1.045
32.8815

1.218
30.6747
1.118
30.8103
1.180
30.9339
1.654
32.7697
1.042
32.8885

1.270
30.6829
1.104
30.8168
1.124
32.6461
1.581
32.7755
1.040
32.8943

1.320
30.6907
1.093
30.8250
1.144
32.6544
1.505
32.7820
1.041
32.9003

1.378
30.6991
1.086
30.8277
1.173
32.6617
1.452
32.7878
1.045
32.9061

1.423
30.7068
1.073
30.8357
1.195
32.6677
1.376
32.7952
1.054
32.9122

1.437
30.7141
1.061
30.8423
1.219
32.6744
1.328
32.8010
1.055
32.9180

1.439
30.7207
1.056
30.8503
1.257
32.6803
1.281
32.8071
1.067
32.9239

1.441
30.7277
1.053
30.8562
1.303
32.6870
1.243
32.8129
1.074
32.9297

1.434
30.7342
1.046
30.8640
1.341
32.6929
1.215
32.8188
1.081
32.9364

1.435
30.7416
1.055
30.8698
1.401
32.7002
1.195
32.8247
1.087
32.9422

1.418
30.7481
1.055
30.8757
1.460
32.7062
1.168
32.8311
1.096
32.9482

1.372
30.7569
1.063
30.8824
1.570
32.7171
1.159
32.8375
1.116
32.9540

1.326
30.7635
1.066
30.8882
1.654
32.7254
1.133
32.8439
1.163
32.9698

1.276
30.7704
1.079
30.8941
1.730
32.7321
1.110
32.8499
1.182
32.9757

1.245
30.7769
1.097
30.9045
1.749
32.7379
1.089
32.8557

1.203
30.7836
1.108
30.9104
1.744
32.7446
1.079
32.8616

2455800+
2455800+
2455800+
2455800+
2455800+

1.163
30.6536
1.222
30.7908
1.188
30.9285
1.735
32.7509
1.108
32.8620

1.198
30.6608
1.177
30.7977
1.205
30.9344
1.741
32.7579
1.098
32.8678

1.227
30.6681
1.170
30.8042
1.238
30.9415
1.720
32.7638
1.090
32.8761

1.261
30.6754
1.150
30.8109
1.145
32.6468
1.657
32.7702
1.081
32.8819

1.312
30.6835
1.133
30.8175
1.172
32.6550
1.595
32.7760
1.073
32.8890

1.355
30.6913
1.143
30.8256
1.191
32.6623
1.511
32.7825
1.069
32.8948

1.419
30.6997
1.104
30.8364
1.213
32.6682
1.458
32.7883
1.078
32.9008

1.463
30.7074
1.097
30.8429
1.241
32.6749
1.394
32.7957
1.074
32.9066

1.481
30.7148
1.086
30.8508
1.291
32.6809
1.339
32.8014
1.085
32.9126

1.480
30.7213
1.089
30.8566
1.330
32.6875
1.300
32.8076
1.085
32.9184

1.486
30.7283
1.085
30.8644
1.372
32.6935
1.266
32.8134
1.098
32.9244

1.494
30.7349
1.084
30.8762
1.422
32.7007
1.252
32.8193
1.101
32.9302

1.482
30.7422
1.092
30.8828
1.491
32.7067
1.216
32.8251
1.106
32.9368

1.464
30.7488
1.095
30.8887
1.584
32.7175
1.205
32.8316
1.119
32.9426

1.410
30.7576
1.103
30.8946
1.680
32.7258
1.190
32.8380
1.152
32.9545

1.357
30.7641
1.129
30.9050
1.738
32.7325
1.155
32.8444
1.189
32.9703

1.313
30.7710
1.146
30.9109
1.741
32.7383
1.135
32.8504
1.215
32.9761

1.286
30.7776
1.151
30.9167
1.734
32.7451
1.120
32.8562
1.179
32.9763

1.242
30.7842
1.171
30.9227

2455800+
2455800+
2455800+
2455800+
2455800+

1.181
30.6541
1.236
30.7913
1.224
30.9289
1.745
32.7583
1.135
32.8765

1.210
30.6613
1.212
30.7982
1.247
30.9348
1.736
32.7642
1.124
32.8823

1.238
30.6687
1.191
30.8048
1.264
30.9419
1.669
32.7706
1.118
32.8952

1.274
30.6759
1.177
30.8114
1.161
32.6473
1.608
32.7764
1.108
32.9011

1.315
30.6841
1.161
30.8180
1.211
32.6553
1.538
32.7829
1.113
32.9070

1.372
30.6918
1.141
30.8261
1.227
32.6626
1.479
32.7887
1.118
32.9130

1.426
30.7002
1.138
30.8369
1.239
32.6686
1.416
32.7961
1.131
32.9188

1.476
30.7079
1.129
30.8434
1.257
32.6752
1.368
32.8019
1.148
32.9248

1.486
30.7153
1.120
30.8512
1.329
32.6812
1.332
32.8080
1.145
32.9306

1.501
30.7218
1.113
30.8570
1.348
32.6878
1.296
32.8138
1.148
32.9372

1.501
30.7288
1.104
30.8648
1.402
32.6938
1.274
32.8197
1.155
32.9430

1.506
30.7354
1.121
30.8707
1.452
32.7011
1.250
32.8255
1.168
32.9491

1.516
30.7427
1.129
30.8832
1.510
32.7071
1.232
32.8320
1.184
32.9549

1.485
30.7493
1.138
30.8891
1.606
32.7179
1.227
32.8384
1.240
32.9707

1.424
30.7581
1.136
30.8950
1.689
32.7262
1.196
32.8448
1.253
32.9765

1.379
30.7646
1.157
30.9054
1.733
32.7329
1.177
32.8508

1.345
30.7715
1.174
30.9113
1.766
32.7387
1.164
32.8566

1.286
30.7781
1.185
30.9172
1.748
32.7455
1.157
32.8624

1.260
30.7847
1.206
30.9231
1.751
32.7513
1.134
32.8682

HJD is the Heliocentric Julian Date.

3. Finding Chart

Our comparison star () was GSC 2300 0035, [(2000) = 01 h 27 m 41.0660 s, (2000) = +33° 51′ 55.298′′  , Guide 9]. The check star () was GSC 2300 0053, [ = , (2000) = +38° 57′′ 24.156′′  , , Guide 9]. We include a finding chart of these stars and the variable () in Figure 2.

Figure 2: Finding chart, V530 And variable (), comparison (), and check ().

4. Period Determination

Two mean times of minimum light were determined from our observations. These include HJD and HJD . We determined 9 more times of low light from the NSVS catalog data set for object number 6447718. We combined this data with Khruslov’s ephemeris to calculate the following new ephemeris (see Table 2 for the calculation): The following is from our Wilson-Devinney program light curve solution:

Table 2: Times of minimum light, V530 And.

No.
EPOCHS
Cycles
Weight
O-C

1
51335.3990
−7791.5
0.1
0.0390
NSVS

2
51335.4000
−7791.5
0.1
0.0400
NSVS

3
51442.1819
−7606.5
0.1
0.0367
NSVS

4
51442.1822
−7606.5
0.1
0.0370
NSVS

5
51454.3080
−7585.5
0.1
0.0413
NSVS

6
51454.3091
−7585.5
0.1
0.0423
NSVS

7
51507.4016
−7493.5
0.1
0.0309
NSVS

8
51507.4019
−7493.5
0.1
0.0312
NSVS

9
51518.3594
−7474.5
0.1
0.0216
NSVS

10
51479.6320
−7541.5
1.0
−0.0323
Khruslov (2008) [1]

11
55830.7281
−3.5
1.0
0.0013
Present observations

12
55832.7460
0.0
1.0
−0.0010
Present observations

Each time of minimum light and low light used in the calculation and depicted in Figure 3 is given in Table 2 along with their residuals. Equation (3) is from the programs iterative fit to the light curve data while (2) is a least squares fit to the minima. The NSVS minima are times of low light and carry large uncertainties. We include both ephemerides since they are the best we have at this time.

Figure 3: The - residuals are calculated from (2) and appear in Table 2. The residuals on the left are low precision points with low weights from times of low light.

What we have here is an initial period study. The Wilson programs determination (3) may be better than the one determined from the minima. Further observations, over the course of 10 years or more, are needed to better determine a precision ephemeris and the nature of the period behavior of the system.

5. Light Curves

The light curves were folded , , , , , (), (), and () color curves using (2). They are given in Figures 4(a), 4(b), and 4(c).

(a)

(b)

(c)

Figure 4: (a) , delta mags of V530 And phased with (2). (b) , delta mags of V530 and phased with (2). (c) , delta mags of V530 And Phased with (2).

Light curve characteristics are given in Table 3. The primary light curve amplitudes of this EB system average 0.8−0.6 mags from to , respectively, and 0.4 mags in the secondary amplitudes. A small O’Connell effect (MAX II-MAX I) [3] of about 1% exists with MAX II being slightly depressed. Thus, we expect some spot activity. The secondary eclipse showed a time of constant light of 41.5 minutes. This means that the eclipses are total and that the more massive, larger star is the hotter component. This is to be expected in normal stellar evolution. We also note that this binary is not one of the common W-type shallow contact types.

Table 3: Light curve characteristics, V530 And.

Filter
Phase 0.25
MAX I, MAG
Phase 0.75
MAX II, MAG

Filter
Phase 0.5
MIN II, MAG
Phase 0.0
MIN I, MAG

Filter
MIN I-MAX I
MAX II-MAX I
MIN II-MAX I
MIN I-MIN II

6. Synthetic Light Curve Solution

2MASS Photometry yielded a value of ≈0.19. From this, we assumed that the primary component was ~F2 type, with a surface temperature of ≈7000 K [4] so this value was used for the primary components temperature in modeling. The light curves were premodeled with Binary Maker 3.0 [5]. From this work, it was determined that the synthetic light curve fits would be done in Mode 4, semidetached with component one filling its Roche lobe. The parameters resulting from this premodeling were used as starting values for the Wilson-Devinney program [6–9]. The secondary component remained under-filling its Roche lobe throughout the iterations. Adjusted parameters were those with parentheses in Table 4. A simultaneous 5-color synthetic light curve solution was undertaken with the Wilson-Devinney program. No q-search was needed since the curves display total eclipses. A mode 3 solution (contact binary) was also run with much poorer goodness of fit parameters.

Table 4: Light curve solution, V530 And.

Parameters
Values

, , , , (nm)
360, 440, 550, 640, 790

,
0.644, 0.643, 0.231, 0.160

,
0.572, 0.647, 0.267, 0.183

,
0.655, 0.735, 0.278, 0.165

,
0.728, 0.797, 0.269, 0.108

,
0.817, 0.853, 0.215, −0.018

,
0.859, 0.855, 0.208, −0.209

,
0.32

,
0.5

Inclination (°)

, (K)
7000,

,
2.63423,

Fill-outs:
100%, %

JDo (days)

Period (days)

, (pole)
,

, (point)
,

, (side)
,

, (back)
,

Cool Spot

Spot 1 on STAR 1

    Colatitude (°)

    Longitude (°)

    Spot radius (°)

    Spot -factor

Spot 2 on STAR 1

    Colatitude (°)

    Longitude (°)

    Spot radius (°)

    Spot -factor

7. Discussion

We find that V530 And is a V1010 Oph type near contact binary. The primary, more massive component is filling its Roche lobe and the secondary is under-filling. This means that the binary is likely achieving contact for the first time. The temperature difference () in components is ~500 K. The mass ratio was found to be somewhat extreme, . The potentials are given as s, and the -values are the relative flux from each stars. The values of are the gravity darkening’s, s are the two dimensional limb darkening, and the s are the dimensions of the Roche lobes. The more massive star is filling its Roche lobe with a fillout, , of 100% while the smaller star is just under-filling with a fillout of 99% calculated by potentials. Thus, the state of the star is near contact or has just come into contact. We reason this is true because of the temperature disparity. It is of interest that both surface spots stayed remarkably stable throughout the iterations and are near the points of both stars. There may be some thermodynamic reason why the hemispheres of dark spots are facing each other. The solution is seen overlaying the normalized flux curves shown in Figures 5(a), 5(b), and 5(c). The complete numeric values for the solution are given in Table 4. Four phases, at orbital quadrature’s, of the Roche-lobe model of the binary and for the dark spots, are shown as in Figures 6(a), 6(b), 6(c) and 6(d). Phase zero shows the total eclipse.

(a)

(b)

(c)

Figure 5: (a) , synthetic light curve solutions overlaying the normalized flux curves. (b) , synthetic light curve solutions overlaying the normalized flux curves. (c) , synthetic light curve solutions overlaying the normalized flux curves.

(a)

(b)

(c)

(d)

Figure 6: (a) Geometrical surface of V530 And, phase 0.0. (b) Geometrical surface of V530 And, phase 0.25. (c) Geometrical surface of V530 And, phase 0.50. Note total eclipse. (d) Geometrical surface of V530 And, phase 0.75.

8. Conclusion

Thus, the components are apparently F2V and F5V spectral types. Despite the fairly early spectral types, with the primary star nearly A-type, the presence of the large cool magnetic spots on both stars reveal that they have convective atmospheres and thus would be classified as solar type. It is a near contact, totally eclipsing, binary. Thus, the binary will likely soon come into contact through the process of magnetic braking due to solar type winds leaving the stars along the stiff magnetic field lines [10].

Acknowledgments

The authors thank USC, Lancaster, for their support of thier membership in NURO for the past 8 years, the American Astronomical Society for its support through its former small research program, and the Arizona Space Grant for the partial support for thier student’s travel.

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